More particularly, the instant invention relates to a syringe of the above mentioned type comprised by a main cylindrical, hollow body, containing the medicine to be administered, and through which a coaxial plunger is located. In all cases the lower base of said main cylindrical body has an opening through which the rear end of said coaxial plunger projects, and having an annular flange in order that the user may push or pull manually the plunger, according to the desired action. The inner end or head of the plunger tightly fits inside the walls and at the bottom of said main body, such that the variable volume chamber defined therein is always tight and isolated from the outside. Said bottom has, in turn, an outer frusto-conical hollow and coaxial nozzle converging towards its outer end, constituting the plugging means for coupling and fixing the injection needle.
The novelty of the invention resides in that the syringe has two chambers: one containing the powdered product and the other the diluent. i.e. it is capable of diluting and administering simultaneously powdered drugs.
Such a functional feature, in a disposable syringe, is a consequence of various novel constructive characteristics.
It is known that, at present, administration of powdered drugs requires prior preparation of the mixture before introducing it into the syringe, this implying contamination risks even though this procedure is carried out carefully; in order to be diluted, such powdered drugs are subject to handling which may introduce contaminants, said handling comprising solid and solvent pouring from one container to another and then introducing the mixture into the syringe.
The instant invention always warrants the use of new syringes and needles, thus preventing any possibility of contamination during preparation, as a consequence of the elimination of steps and containers used for preparing and administering this kind of medicines, the operation being carried out completely inside the syringe, in a single step.
The invention also affords a quick operation since preparation and application times are shortened, assuring at the same time the exact dosage of the drug. It also avoids accidental cuts on the user's fingers since powdered drug and solvent glass containers are not employed.
The above mentioned advantages are a result of the novel syringe of the invention, which has a main body defining two aligned and coaxial chambers, from which that closer to the needle contains the powdered drug, and the second is a hollow cylinder body tightly displacing through the inner part of the former chamber and including the liquid diluent. Further, through the interior of this second chamber, the syringe plunger displaces; between both chambers there is a elastomeric and tight plug, integral to the lower chamber body, tightly and slidably fitted on the inner cylindrical surface of the upper chamber body. This plug has a longitudinal central conduit communicating both chambers such that liquid contained in the lower chamber may penetrate the upper chamber when the syringe plunger is actuated, the mixture obtained is stirred until total dilution of the solid occurs; then injection is effected by continuously pushing the plunger which, at this time, also displaces said longitudinal central plug.